A train company's services in part of the East Midlands were severely disrupted on Sunday because of a shortage of drivers.
Sunday working for the on-train staff is voluntary.
This week Central Trains bosses said an "exceptional" number of drivers had decided they would not go in.
Services between Nottingham and Skegness, Birmingham and Lincoln were limited - with buses operating instead of some trains.
Ged Burgess from Central Trains said: "Sundays don't form part of the contract for the working week for train crew and we have volunteers. Generally we have enough volunteers to cover the services but this Sunday we're not going to."
Travellers are being warned that more disruption is likely over the festive period - with 500 guards preparing to walkout on Christmas Eve, New Years Eve and New Years Day, in an ongoing dispute over pay and holidays.